At an early stage in their manufacture, vehicle bodies are commonly dipped in one or more treatment baths containing cleaners, rust inhibitors, and primers. As the vehicle body leaves such a bath, excess liquid must be drained quickly from its sheet metal surfaces so that the body may be advanced into a drying oven and proceed to further processing stations. To facilitate the draining of the coating materials (generally referred to herein as "paints"), such a body is provided with drain openings. It is essential that those openings later be sealed in order to prevent carbon monoxide and water from entering the passenger compartment when the completed vehicle is put to use. For that purpose, and to help reduce noise transmission, protective shields are clipped in place over the drain openings and sealant pads or covers are then applied over the seams or joints between the shields and the body panels in which the drain openings are provided.
The shields with their spring clips have the disadvantages of being relatively expensive to make. Also, because they rely on spring elements to hold them in position, at least initially, there is some risk that they might not be securely attached during installation or become detached following installation. While such risks are reduced by the sealant covers that are subsequently applied over each shield, the need to apply such covers in subsequent operations is also undesirable because it increases production and labor costs. A main aspect of this invention lies in providing an improved system for sealing such paint drain openings of automotive vehicles. The closure used for that purpose is relatively simple in construction and is easily and quickly applied either by robot or by a worker using suitable power equipment. The closure is initially retained in place only by a positive interlock between the parts, but that interlock is capable of withstanding removal forces far greater than those to which the finished assembly would normally be subjected. A highly effective hermetic permanent seal is then formed during a subsequent baking or heat-drying operation in which a thermoplastic adhesive ring or gasket, interposed between the flange of the sealant plug and the surface of the body panel about the drain opening, is softened. Since the thermoplastic sealant ring is pre-mounted upon the sheet metal plug, the plug and ring (together referred to as the "closure") are installed simultaneously, thereby reducing manipulative steps and production costs.
Briefly, the plug is formed from a single piece of deformable sheet metal, is of inverted hat-shaped configuration, and has an imperforate bottom wall, a continuous side wall extending upwardly from the periphery of the side wall, and a flat perimetric flange extending outwardly from the upper limits of the side wall. A thermoplastic sealant ring is secured to the underside of the flange.
The plug is preferably circular or oval in shape and has a bottom wall that may be flat although, ideally, it is dome-shaped with the central portion of the dome being at the same level as the perimetric flange. In a preferred embodiment, the side wall has at least a pair of perimetrically-spaced indentations or recesses extending to the plug's bottom surface. Integral protuberances are disposed in those indentations, the protuberances extending outwardly a distance that does not exceed a circumscribing projection of the contour of the surfaces of the side wall immediately adjacent each indentation. Such a plug is "universal" in its application to the extent that it may be locked in a panel opening of regular oval or circular contour by the outward dimpling of the plug's side wall or, alternatively, in an opening that is of regular or oval shape except for the provision of circumferentially-spaced locking tabs or shoulders that engage the protrusions of the plug to securely hold the plug in place after it has been inserted and rotated a small fraction of one full turn.
The dimpling tool for applying the closure plug has a head that is dimensioned to be inserted into the cavity of the plug. Magnetic elements or other suitable means are used for temporarily holding the closure upon the head of the tool. By automation or manual guidance, the tool is directed to insert the bottom and side walls downwardly into a drain opening. When fully inserted in the opening, the sealant ring carried along the underside of the flange engages the upper surface of the body panel and the side wall of the plug extends downwardly beyond the body opening. With the head of the tool remaining within the cavity of the plug, the tool is actuated to force a plurality of cam-driven dimpling elements radially outwardly to deform the side wall of the plug and produce external nubs or projections that tightly clamp the plug in position.
The closure and its method of attachment are ideally suited for automation. The same holes or openings used for the draining of paint prior to attachment of the closures may be used for supporting, guiding, and positioning the vehicle body. Precise location of the body may be achieved utilizing the drain holes and, with the body so positioned, the holes may be automatically plugged and sealed in the manner described.
Other advantages, features, and objects of the invention will become apparent from the drawings and specification.